Multicolor press and process with impression cylinder having axially shiftable sheet grippers

ABSTRACT

A multicolor sheet offset printing process and a printing press in which a sheet is clamped upon an impression cylinder and printed with one color and then shifted on the same cylinder in the axial direction thereof to one or more further printing stations in each of which it is printed with another color.

United States Patent 1 Ras [ 11 3,744,415 [451 July 10,1973

MULTICOLOR PRESS AND PROCESS WITH IMPRESSION CYLINDER HAVING AXIALLY SHIFTABLE SHEET GRIPPERS Inventor: Max Junghans Ras, Kloten, Zurich,

Switzerland Assignee: J. G. Mailander, Stuttgart, Germany Filed: Aug. 16, 1971 Appl. No.: 171,918

Foreign Application Priority Data Aug. 17, 1970 Switzerland 12297/70 U.S. Cl 101/177, 101/211, 101/232 Int. Cl. B411 5/02, B41f 21/04 Field of Search 101/174, 177, 183,

[56] References Cited UNITED STATES PATENTS 1,095,528 5/1914 Sheldon 101/174 Primary Examiner-J. Reed Fisher Attorney-Arthur O. Klein ABSTRACT A multicolor sheet offset printing process and a printing press in which a sheet is clamped upon an impression cylinder and printed with one color and then shifted on the same cylinder -inthe axial direction thereof to one or more further printing stations in each of which it is printed with another color.

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- MAX ms By [5 78 4 ATTORNEy MULTICOLOR PRESS AND PROCESS WITH IMPRESSION CYLINDER HAVING AXIALLY SHIFTABLE SHEET GRIPPERS The present invention relates to a multicolor offset printing process which also permits proofing operations, and to a sheet press for carrying out this process.

It is conventional in multicolor offset printing to mount several one-color sheet presses directly behind each other so that the sheet to be printed runs out of one press into the next. Substantially the same occurs if the individual one-color printing units are mounted in a row behind but spaced from each other. After a sheet has then been printed in one unit in one color it is conveyed by grippers over intermediate drums or chains from the impression cylinder of this unit to the impression cylinder of the following unit and so forth until it arrives at the delivery station.

This manner of carrying out the successive printing.

operations is rather expensive since it requires a considerable amount of machinery and moreover a considerable time for carrying out the necessary adjustments. The plate cylinders of the printing units following the first unit must be very accurately adjusted in lateral and peripheral directions relative to those of the preceding units. Furthermore, it is necessary to mount the sheet newly for each color which must be done at such a high degree of accuracy that it is practically impossible to do this on a larger number of sheets with equalaccuracy which has the result that the images printed on the different units are hardly ever accurately in registry.

With the known printing presses it was also very uneconomical and difficult to produce proofs and small series of multicolor prints by offset printing. For multicolor rotary offset printing it is also essential first to make a series of proofs and proofing scales. For this purpose it has been necessary prior to this invention to roll a blanket cylinder for each of the required colors along a sheet lying on a flat support. Eachcolor then dried before the next color was printed thereon. This procedure required a considerable length of time and also had the disadvantage that any wet on wet printing was practically impossible. Consequently, the results attained in such a proofing process could hardly be used as evidence as to how a large series of multicolor prints would subsequently appear when printed wet on wet by rotary printing or multicolor sheet printing.

The making of proofs according to the conventional method is therefore sensible only if it is done by experts with large experience which are capable to judge how the density of the color as selected for the proof will compare with the color as produced in the following rotary printing process.

Similar conditions prevail when producing very small series of prints which prior to this invention had to be made on proofing presses which operate according to the principle as just described. 7

his an object of the present invention to provide a sheet-fed multicolor offset printing process which substantially eliminates all of the disadvantages of the known processes as previously described and especially reduces the adjusting and registering work and permits a quick wet on wet printing and also small series of mu]- ticolor prints to be produced which was hardly possible with any of the known processes and with the machines with which these processes were carried out.

For attaining this object, the present invention provides that after a sheet has been clamped upon an impression cylinder in a first printing position and one of the colors has been printed thereon, the sheet is shifted on the impression cylinder in the axial direction thereof to a second printing position in which a further color is printed upon the sheet. This procedure is thereafter repeated until all colors are printed upon the same sheet.

This new process not only eliminates the previous need of repeatedly clamping the sheet to be printed, but since all colors may be printed in a single press, it also eliminates the previous need of adjusting several impression cylinders relative to each other. Furthermore, since between two successive printing operations it is only necessary to shift the sheet to be printed along the impression cylinder in the axial direction thereof, the different colors may be printed in quick succession upon each other so that actually a wet on wet printing may be carried out. Finally, it is also of advantage that only a single press is required for producing multicolor prints very easily and accurately. I

It is a further object of the invention to provide a sheet or sheet-fed offset printing press which is espe-' cially designed for carrying out the new process. For attaining this object, the press according to the invention comprises a plate cylinder, a blanket cylinder and an impression cylinder all of which are made of a length which amounts at least to a multiple of the width of the sheet to be printed and is at least in accordance with the number of colors which are to be printed on this sheet. Another feature of the invention consists in providing the impression cylinder with a sheet gripping mechanism which is slidable along this cylinder. A further important feature of the invention consists in providing the blanket cylinder in the form of several segments which are mounted laterally adjacent to each other on the shaft of this cylinder and are peripherally offset relative to each other and each of which is operatively associated with one of several printing plates 7 which are mounted adjacent to each other on the plate cylinder.

A very important advantage of such a press is the fact that it requires considerably less space than the conventional sheet offset presses for multicolor printing. Furthermore, the necessary adjusting operations require very little time, much less than they required for the repeated adjusting operations on the succession of printing 'units as were previously necessary. Another important advantage of the invention is the fact that the new press permits wet on wet printing so that the finished print is worth of being compared with a print which has been directly produced by a rotary printing process. Last not least, the small amount of work and time which are required for carrying out the necessary adjustments and also the possibility of producing wet on wet prints permit an economic printing also of small series of prints.

The features and advantages of the present invention will become more clearly apparent from the following detailed description thereof which is to be read with reference to the accompanying drawings, in which:

FIG. 1 shows, partly in section, a side view of a fourcolor sheet offset press according to the invention, while FIG. 2 shows diagrammatically and likewise partly in section a top view of the same press, in which, however,

the individual rollers and cylinders are shown in development.

As illustrated. in these drawings, the sheet offset press according to the invention comprises a frame 1 in which a plate cylinder 2 is rotatably mounted on which several printing plates 3a to 3a one for each color are mounted laterally adjacent to each other. Following this plate cylinder 2 a blanket cylinder 4 and following the latter an impression cylinder 6 are rotatably mounted in the frame 1. The impression cylinder 6 carries a gripper carriage 8 which is slidable in the axial direction of this cylinder and is provided with grippers 7 for tightly clamping each sheet to be printed. Preceding the plate cylinder 2 an inking assembly 10 is provided which comprises four inking units 10a to 10d each of which is provided with its own ink cup or ink box 9a to 9d and its own ink applying roller 11. These inking units may be of a conventional type of construction except insofar as they are arranged so that the corresponding rollers of the adjacent inking units with the exception of the doctor rollers are mounted on a common shaft which considerably simplifies the bearing and driving means for these rollers.

The dampening assembly 13 is designed similar to the inking assembly 10 insofar as it comprises four equal dampening units laterally adjacent to each other, and all corresponding rollers of these units with the exception of the doctor rollers are again mounted on a common shaft.

The plate cylinder 2 is substantially of a cylindrical shape and provided at two points which are located substantially diametrically opposite to each other with recesses 15 and 16 which extend in the longitudinal direction of cylinder'2. Recess 15 contains a registering mechanism 17 by means of which the leading ends of plates 3a to 3d may be clamped upon metal strips 18. Into the trailing ends of these plates, however, a tension strip (not shown) is hooked which is acted upon by a tension spring 12 which is mounted within the recess 16, so that the printing plates 3a to 3d are tightly and uniformly applied upon the peripheral surface parts of plate cylinder 2. It is, of course, to be understood that this manner of mounting the printing plates requires them to be sufficiently flexible. As illustrated in FIG. 2, all of these plates 30 to 3d are mounted on cylinder 2, so that their longitudinal sides are adjacent to each other and their leading ends are located on the same transverse generatrix of cylinder 2.

FIG. 1 further indicates that each of the printing plates 3a to 3d only has a length equal to approximately one third of the circumference of plate cylinder 2.

Each of the printing plates 30 to 3d is to be used for printing one color and is for this purpose associated with one of the dampening and inking units as already described.

The blanket cylinder 4 is substantially composed of four laterally adjacent segments'19a to 19d each of which is offset at an angle of 90 in the peripheral direction relative to the adjacent segment. Each of these segments is clamped tightly upon a common drive shaft 20 by meansof'a semicircular shell 21, as shown in FIG.

1 Each segment 19a to 19d is covered by a rubber blanket 5a to 5d each of which is secured by clamping strips and bolts 22 to the respective segment.

In FIG. 1 it may be clearly seen that the outer peripheral surface of each segment 19a to 19d only forms approximately one fourth of the entire circumference of the blanket cylinder 4 so that, as seen in a development as shown in FIG. 2, the segments and the rubber blankets 5a to 5d thereon have a step-shaped arrangement. This arrangement of the segments 19a to 19d and their blankets 5a to 5d on drive shaft 20 also results in a balanced unit because the unbalance which is produced by one of the segments, for example, the segment 19a, is compensated by the unbalance which is produced by the diametrically opposite segment, for example, the segment 19c.

Each blanket 5a to 5d has a length substantially corresponding to the length of one of the printing plates 34 to 3d. Since each of these plates covers only approximately one third of the circumference of the plate cylinder 2, but the rubber blankets 5a to 5d cover successively the entire circumference of the blanket cylinder 4 which is defined by the segments 19a to 19d, it is evident that the diameter of the plate cylinder 2 has a ratio of three to four to the diameter of the blanket cylinder 4.

The blanket cylinder is followed by the impression cylinder 6 which, as already mentioned, is provided with a carriage 8 carrying the grippers 7 and is slidable in the longitudinal direction of cylinder 4 for shifting a sheet 24 to each of four adjacent printing positions 24a to 24d. The gripper carriage is of this purpose longitudinally movable on railsin a manner not particularly shown within a recess 23 in the peripheral surface of the impression cylinder 6., To the opposite ends of carriage 8 a belt 25 is secured which passes similarly to an endless belt around two guide rollers which are mounted on the front and rear ends of cylinder 6 and one of which is connected by a slipper clutch 26 to a miterwheel gearing 27 which is mounted in a manner not shown on the end of cylinder 6, as may be seen at the right upper side of FIG. 2. One wheel of the miterwheel gearing 27 is directly connected to a pinion 28 which, in turn, meshes with a large gear 29. This gear 29 is freely rotatable on the shaft of cylinder 6 and driven by a pinion 30 as shown in FIG. 1 which, in turn, is driven through a chain 44, a reduction gearing 39 and a V-belt 38 by a common motor 37.

The speed ratios of the elements as last described are designed so that the continuously rotating gear 29 rotates in the same direction as the impression cylinder 6 and has a lower speed than the normal speed of the latter. If therefore the impression cylinder 6 is stopped and the miter-wheel gearing 27 and the pinion 28 therefore do not revolve, gear 29 will drive the pinion 28 in that direction which corresponds to the direction of movement of the stringer of belt 25 to which the carriage 8 is secured, that is, downwardly as seen in FIG. 2. This direction of movement of belt 25 continues as long as the carriage 8 has not as yet reached the printing position 24a. As soon as this occurs, carriage 8 abuts against a stop 51 which prevents its further movement and also stops the belt 25 since the slipper-clutch 26 through which the belt is normally driven will then slip.

If, however, the impression cylinder 6 starts to turn and to run at its normal speed, gear 29 although continuing to rotate in the same direction appears to run in the opposite direction because of its own lower speed, as seen from the rotating impression cylinder 6. This has the result that pinion 28 will roll in the opposite direction along gear 29 and will thereby reverse the direction of movement of belt 25 which will then tend to take the carriage 8 along toward the printing position 24a, that is, upwardly as seen in FIG. 2. However, carriage 8 cannot as yet be shifted from the printing position 24a to the printing position 24b since it is prevented from doing so by one of several stops 32. One of these stops 32 is provided for each of the printing positions 24a, 24b and 24c, and all of them are rigidly secured to a common shaft 31 which is pivotably mounted in recess 23 in the peripheral surface of cylinder 6. One end of shaft 31 projects beyond the end of the impression cylinder, that is its lower end as seen in FIG. 2, and it carries a control arm 33 which during each revolution of cylinder 6 abuts against a stop 34 which carries a roller and is mounted in a stationary position on the frame 1. When the arm 33 abuts against this stop 34, shaft 31 will be pivoted for a short time in the clockwise direction with the result that all stops 32 on shaft 31 will be pivoted out of the path of travel of carriage 8. Carriage 8 is thus released and will beshifted by belt 25 in the direction toward the printing position 24b. As soon as the control arm 33 has passed the stop 34, a spring, not shown, will tend to pivot the shaft 31 and thus also the stops 32 back to their original positions. However, the stops 32 cannot return to their original positions until carriage 8 no longer prevents them from doing so. This occurs immediately before the carriage reaches the printing position 24b. The stops 32 are then again quickly pivoted upwardly and at the beginning of the second revolution of cylinder 6, carriage 8 and thus also the sheet 24 will have reached exactly the printing position 24b where the carriage, held by the associated stop 32, will remain untilsheet 24 has completely rolled over the respective rubber blanket 5b. The same operations as above described will then be repeated between the printing position 24b and the printing position 240. The same also occurs during the transfer of the sheet from the printing position 24c to the printing position 24d, except that the printing position 24d is determined by a fixed stop 35 which is mounted at the end of the impression cylinder 6. After carrying out four revolutions, cylinder 6 is stopped, whereby the continuously rotating gear 29 will again run ahead of cylinder 6 with the result that belt 25 will reverse its direction of movement and shift the carriage 8 back to its original position. This is easily possible due to the fact that the stops 32 are designed so as to permit the carriage 8 to travel over them in this direction. This is indicated in FIG. 2 by the free ends of stops 32 being made of a beveled shape.

Of course, the gripper carriage 8 could also be shifted axially along the impression cylinder 6 by other suitable means, for example, by a stepping motor which is actuated after each complete revolution of cylinder 6, or by a continuously running electric motor the movement of which is transmitted to carriage 8 at the required times by an electromagnetic clutch.

It is also possible, for example, by retracting the stop 34 into the wall of frame 1', to shift the carriage 8 to less than all four printing positions when the impression cylinder has carried out less than four revolutions. It will that the peripheral speeds of all cylinders are exactly equal and the adjacent cylinders rotate in opposite directions to each other. Thus, blanket cylinder 4, as seen in FIG. 1, turns in the clockwise direction, while the plate cylinder 2 and the impression cylinder 6 turn in the counterclockwise direction.

The driving diagram of the machine may be seen in FIG. 1. Gear 42 (FIG. 2) for driving the blanket cylinder 4 meshes with the smaller pinion of an electromagnetic brake 50, the larger pinion of which meshes with a gear 40a which is adapted to be engaged by an electromagnetic clutch mechanism 40. This clutch mechanism 40 is'provided with two further gears which are driven continuously by the motor 37. One of these gears is the sprocket wheel 40b for driving the chain 44' leading to the pinion 30, and the other gear 40c meshes with the smallest gear of a reduction gearing '39 which by a chain 45 drives the inking assembly 10 and also the dampening assembly 13. The reduction gearing 39 is connected to the electric motor 37 by a V-belt 38.-

In the particular embodiment of the invention as illustrated in the drawings, the rates of speed of the plate cylinder 2, the blanket cylinder 4 and the impression cylinder 6 amount to l to to 1 relative toeach other.

The operation of the press proceeds substantially as follows:

It is assumed that the press is in its starting position as illustrated in FIGS. 1 and 2 and that in a previous cycle the rubber blanket 5a has already been inked. A sheet 24 is then inserted by hand or mechanically into the printing position 24a on the impression cylinder 6. The leading edge of sheet 24 then actuates a photoelectric cell 14 which, in turn, actuates a control mechanism, not shown, so as to start one complete cycle of operations of the press. At first, the rotation of an eccentric shaft 36 causes the grippers 7 on carriage 8 to be closed. At the same time, the clutch 40 is engaged and brake is released. Then, during the first revolution of the impression cylinder 6, sheet 24 in the printing position 24a is applied against the rubber blanket 5a and is then transferred to the printing position 24b. In the meantime, blanket cylinder has, however, carried out only a three-quarter revolution and during this movement the rubber blankets 5b, 5c and 5d are rolled along the associated printing plates 3 since the plate cylinder 2 has in the meantime also carried out one complete revolution.

During the second revolution of the impression cylinder 6 the printing position 24b is located exactly opposite to the rubber blanket 5b which will then print the sheet 24. Thereafter, carriage 8 transfers the sheet to the printing position 240. In the meantime, blanket cylinder 4 has carried out another three-quarter revolution, while the plate cylinder 2 has carried out a com.- plete revolution and has thereby inked the blankets 5a, 5c and 5d.

During the third and fourth revolutions of the impression cylinder 6 the same operations occur in the cyclic order of succession.

After four complete revolutions of the impression cylinder 6, brake 50 is actuated by a control mechanism, not shown, and clutch 40 is disengaged so that all cylinders will be stopped. As already described, carriage 8 then moves back to its original position, that is, to a position near the printing position 2411' where the grippers 7 of the carriage will be opened by the return again each of 4 rotation of the eccentric shaft 36 so that the four-color wet-on-wet printed sheet 24 will be released.

After four complete revolutions of the impression cylinder 6 the blanket cylinder 4 has carried out three complete revolutions and the plate cylinder 2 also four complete revolutions.

The printing press and its cylinders are thus again in the same positions as at the beginning of the printing process so that a new printing process may be started.

The speed ratios and dimensional relations between the plate cylinder 2 and the blanket cylinder 4 and the construction of the blanket cylinder 4 in the form of segments have the effect that each printing plate 3a to 3d engages with the associated rubber blanket 5a to 5d only at every fourth revolution of plate cylinder 2, while during the other three revolutions, because of the gear ratio of l to Y4, the printing plates 2 will travel past the blanket cylinder 4 without engaging with the same. On the other hand, at each revolution of plate cylinder 2 each printing plate passes along the associated dampening and inking unit. Consequently, each printing plate is subjected four times to a dampening and inking operation before it transfers theink to the associated rubber blanket. Stated in different words, this means that with a very simple inking mechanism and with only a single inking roller 11 practically the same effect will be attained as with a multicolor inking mechanism with four inking rollers. It is self-evident that this also simplifies the construction of the machine and reduces its cost considerably.

Although my invention has been illustrated and described with reference to the preferred embodiment thereof, I wish to have it understood that it is in no way limited to the details of such embodiment but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim is:

1. A multicolor sheet offset printing process comprising the steps of mounting a sheet in a first axial position on the impression cylinder and gripping the sheet on the impression cylinder in said first position, printing said sheet with one color while the sheet is gripped in said first position, and then while the sheet remains gripped on the impression cylinder shifting said sheet along said impression cylinder in the axial direction thereof to at least one further position and printing said sheet with another color in said further position.

2. A multicolor sheet offset press comprising a plate cylinder, a blanket cylinder and an impression cylinder, means for driving said cylinders, all of said cylinders having a length at least equal to a multiple of the width of a sheet to be printed, said multiple being in accordance with the number of colors to be printed successively on said sheet, gripping means on said impression cylinder for gripping said sheet, guide means for guiding said gripping means together with said sheet from a first position on said impression cylinder in the axial direction along the latter to at least one further position to permit said sheet to be printed with another color in each of said positions, said blanket cylinder comprising a plurality of laterally adjacent segments, each of said segments being laterally and peripherally offset relative to the adjacent segment for a distance at least equal to the axial length and the peripheral length of one segment, and a plurality of printing plates adapted to be mounted on said plate cylinder, each of said segments being operatively associated with one of said printing plates which are mounted laterally adjacent to each other on said plate cylinder.

3. A press as defined in claim 2, in which the circumference of said blanket cylinder is at least equal to a multiple of the length of said sheet.

4. A press as defined in claim 3, further comprisin a plurality of dampening units and inking units, each of said, printing plates on said plate cylinder being preceded by one of said dampening units and one of said inking units, each ofv said units comprising rollers, a common shaft carrying said rollers of said dampening units, and a common shaft carrying said rollers of said inking unit.

5. A press as defined in claim 2, in which said impression cylinder has a recess in its peripheral surface and extending longitudinally of said cylinder, said sheet gripping means comprising a gripper carriage slidable within said recess in the longitudinal direction of said impression cylinder.

6. A press as defined in claim 5, in which said guide means comprise two guide rollers rotatably mounted on the opposite ends of said impression cylinder, an endless belt mounted on and adapted to run over said guide rollers and having two stringers extending substantially parallel to the axis of said impression cylinder, said gripper carriage being secured to said belt, a driving gear, means for driving said gear continuously so as to have a peripheral speed lower than the peripheral speed of said impression cylinder, and a slipper clutch connecting said driving gear to one of said guide rollers for driving the same when said clutch is engaged.

7. A press as defined in claim 2, in which said plate cylinder and said impression cylinder have an equal diameter, said printing plates being adapted to be mounted on said plate cylinder so that their longitudinal sides are adjacent to each other.

8. A press as defined in claim 7, in which the equal diameter of said plate cylinder and said impression cylinder has a ratio of three to four relative to the diameter of said blanket cylinder.

t t fl I8 

1. A multicolor sheet offset printing process comprising the steps of mounting a sheet in a first axial position on the impression cylinder and gripping the sheet on the impression cylinder in said first position, printing said sheet with one color while the sheet is gripped in said first position, and then while the sheet remains gripped on the impression cylinder shifting said sheet along said impression cylinder in the axial direction thereof to at least one further position and printing said sheet with another color in said further position.
 2. A multicolor sheet offset press comprising a plate cylinder, a blanket cylinder and an impression cylinder, means for driving said cylinders, all of said cylinders having a length at least equal to a multiple of the width of a sheet to be printed, said multiple being in accordance with the number of colors to be printed successively on said sheet, gripping means on said impression cylinder for gripping said sheet, guide means for guiding said gripping means together with said sheet from a first position on said impression cylinder in the axial direction along the latter to at least one further position to permit said sheet to be printed with another color in each of said positions, said blanket cylinder comprising a plurality of laterally adjacent segments, each of said segments being laterally and peripherally offset relative to the adjacent segment for a distance at least equal to the axial length and the peripheral length of one segment, and a plurality of printing plates adapted to be mounted on said plate cylinder, each of said segments being operatively associated with one of said printing plates which are mounted laterally adjacent to each other on said plate cylinder.
 3. A press as defined in claim 2, in which the circumference of said blanket cylinder is at least equal to a multiple of the length of said sheet.
 4. A press as defined in claim 3, further comprising a plurality of dampening units and inking units, each of said printing plates on said plate cylinder being preceded by one of said dampening units and one of said inking units, each of said units comprising rollers, a common shaft carrying said rollers of said dampening units, and a common shaft carrying said rollers of said inking unit.
 5. A press as defined in claim 2, in which said impression cylinder has a recess in its peripheral surface and extending longitudinally of said cylinder, said sheet gripping means comprising a gripper carriage slidable within said recess in the longitudinal direction of said impression cylinder.
 6. A press as defined in claim 5, in which said guide means comprise two guide rollers rotatably mounted on the opposite ends of said impression cylinder, an endless belt mounted on and adapted to run over said guide rollers and having two stringers extending substantially parallel to the axis of said impression cylinder, said gripper carriage being secured to said belt, a driving gear, means for driving said gear continuously so as to have a peripheral speed lower than the peripheral speed of said impression cylinder, and a slipper clutch connecting said driving gear to one of said guide rollers for driving the same when said clutch is engaged.
 7. A press as defined in claim 2, in which said plate cylinder and said impression cylinder have an equal diameter, said printing plates being adapted to be mounted on said plate cylinder so that their longitudinal sides are adjacent to each other.
 8. A press as defined in claim 7, in which the equal diameter of said plate cylinder and said impression cylinder has a ratio of three to four relative to the diameter of said blanket cylinder. 